One type of inkjet recording device well known in the art has ink cartridges immovably mounted in the body of the device. Unlike printers having ink cartridges mounted in a carriage, the ink cartridges in a printer having this construction do not move during printing operations, preventing the introduction of air bubbles in the ink and other related problems.
This type of inkjet recording device is commonly provided with cartridge-detecting means for detecting when ink cartridges are mounted. Common types of cartridge-detecting means include optical detecting means such as a transmission-type photosensor having a light-emitting element and a light-receiving element, and electrical detecting means such as an electrical contact switch that detects an ink cartridge through contact with a terminal provided on the ink cartridge. However, since contact problems frequently occur with electrical detecting means such as the electrical contact switches due to ink becoming deposited on the contacts, it is preferable to use photosensors or other optical detecting means to avoid such problems.
Patent Reference 1 discloses an inkjet recording device using transmission-type photosensors to detect when ink cartridges are mounted. The inkjet recording device described in Patent Reference 1 includes cartridge-mounting units (holders) and photosensors disposed one on each holder and provided with a light-emitting element and a light-receiving element at positions opposing each other. Each ink cartridge has a cartridge body storing ink therein. A light-shielding (non-translucent) protruding part extending vertically (in the direction that the ink cartridge is mounted and that ink flows out of the ink cartridge) is formed on a side wall portion of the cartridge body. When an ink cartridge is mounted in a holder, the protruding part on the side wall portion passes between the light-emitting element and the light-receiving element of the photosensor, momentarily blocking light emitted from the light-emitting element, which enables the photosensor to detect mounting of the ink cartridge. When mounting of the ink cartridge is completed, the protruding part is not positioned between the light-emitting element and the light-receiving element in Patent Reference 1 so that the photosensor can additionally detect the presence of ink in the mounted ink cartridge (residual ink detection) when not detecting mounting of the ink cartridge.
Specifically, a light-shielding plate for residual ink detection is provided inside the cartridge in Patent Reference 1. The light-shielding plate is coupled to a hollow float via a pivoting arm so as to pivot along with fluctuations in the residual ink. If sufficient ink remains in the cartridge body, the light-shielding plate and the protruding part for detecting the mount of the cartridge are aligned vertically (in the direction that the ink cartridge is mounted). Accordingly, if an ink cartridge having a sufficient amount of residual ink is mounted in the holder, the protruding part blocks light emitted from the light-emitting element of the photosensor while passing between the light-emitting element and light-receiving element. When mounting is completed, the light-shielding plate is positioned between the light-emitting element and the light-receiving element and, thus, blocks light emitted from the light-emitting element. In other words, a single photosensor can be used both for detecting the ink cartridge and for detecting residual ink.
Thus, Patent Reference 1 employs a construction in which the protruding part for detecting mounting of the cartridge interrupts light emitted from the light-emitting element only when passing between the light-emitting element and light-receiving element during mounting and removal of the cartridge and does not remain positioned between the light-emitting element and light-receiving element after mounting is completed. This configuration intends to provide the photosensor used to detect mounting of the ink cartridge with a separate function (i.e., residual ink detection). However, in light of other design considerations, there is potential for the photosensor to be employed for yet other intentions. Patent Reference 1: Japanese patent application publication No. 2005-254734